The present invention relates generally to the science and technologies of bio-processing. The invention is directed to a quantitative assay method comprising SELDI-TOF Mass Spectrometry to screen for, detect, measure and monitor enzymatic activity in biological samples. SELDI-TOF Mass Spectrometry is an increasingly popular bio-analytical method due in part to the development of techniques that avoid protein fragmentation during the process of volatization (e.g. desorption) and ionization. Other advantages of using SELDI-TOF Mass Spectrometry comprise the ability to identify proteins in a complex sample mixture with high resolution. The use of Mass Spectrometry for protein analysis is described in U.S. Pat. No. 5,118,937 (Hillenkamp et al.), U.S. Pat. No. 5,617,060 (Hutchens et al.) and WO 98/59360 (Hutchens and Yip). However, the present invention uniquely describes the use of SELDI-TOF Mass Spectrometry to accurately quantify enzymatic activity of enzymes with known substrates, or to evaluate effectors (i.e. activators or inhibitors) of such enzymes, directly in native biological samples (e.g. saliva, blood plasma, urine, spinal fluid, or any body fluid, cell or tissue preparations, surfactants).
There is a need for fast, accurate and physiologically relevant methods of analysis of enzymatic activity using unmodified (e.g. native, authentic, natural) substrates of enzymes present in crude biological samples, and, in particular, for methods permitting screening and monitoring of enzymatic biomarkers associated with pathological conditions such as, for example, those resulting from dysfunction of the renin-angiotensin system (RAS). There is also a need for efficiently identifying new therapeutic agents from libraries of compounds targeting such conditions.